In safety tire and wheel assemblies which include inserts of the described type, the insert conventionally comprises a base portion disposed adjacent to the wheel rim and a second portion projecting radially from the rim into the tire cavity or chamber. Upon loss of air pressure in the chamber, the tire tread collapses against the second portion of the insert, such that the insert supports the tire tread with respect to the rim for continued operation of the vehicle. Friction due to relative motion between the tire tread and the tread-supporting portion of the safety insert often causes overheating and destruction of the insert during continued operation. This problem has been alleviated to some extent, but not entirely overcome, by disposition of solid or liquid lubricant along the tread-supporting surface of the insert. However, the relatively soft material of the carcass liner tends to squeeze the lubricant from between the liner surface and insert, so that the engaging insert and tire surfaces eventually are substantially unlubricated.
A goal in the vehicle industry has been to provide a safety tire and wheel assembly which will operate at a vehicle speed of 30 miles per hour over a distance of 30 miles following loss of tire pressure without destruction of the tire or wheel. With the exception of the safety tire and wheel assembly disclosed in the above-referenced copending application, of which this application is a continuation-in-part, and the disclosure of which is incorporated herein by reference, these industry goals or specifications have not been well met by the safety assemblies previously proposed. The safety assembly disclosed in the referenced copending application has been found to satisfy the described industry goal, but comprises a number of assembly components which contribute to the overall weight and expense of the insert.
It has heretofore been recognized in the art that multiple-piece wheel rim assemblies, considered alone or in combination with safety inserts of the above-described type, may present a significant safety hazard if it is attempted to inflate a tire mounted thereon when the various rim assembly components are improperly positioned or seated, or to disassemble the rim when the tire mounted thereon is inflated. This problem is particularly acute in the case of high pressure track tires and the like.
One important object of the present invention is to provide a safety tire and wheel assembly and method, and a safety insert adapted for use therein, which are adapted for operation at a vehicle speed of at least 30 miles per hour for a distance of at least 30 miles following loss of tire pressure, and which are less expensive and lighter in weight than assemblies, methods and inserts heretofore proposed capable of approaching or achieving this industry goal.
Another object of the invention is to provide a safety insert for a pneumatic tire and wheel assembly which is rugged in operation, and yet is light in weight and does not substantially alter the dynamic and static wheel and tire balance characteristics.
A further object of the invention is to provide a wheel rim assembly for tubeless pneumatic tires, including safety tire and wheel assemblies of the above-described type, which prevents inflation of a tire mounted on the rim assembly when the rim assembly components are improperly positioned and/or which automatically vents the tire cavity to atmosphere should disassembly be attempted when the tire mounted thereon is inflated.